The other day we noticed one of our favorite hens Fancypants Johnson, looked like she was having some digestive problems. The other chickens looked normal, so I was just hoping it would resolve itself. Then today we noticed she has a prolapsed oviduct -- it looks like a hemorrhoid. Poor thing. The prognosis isn't too great -- they can have difficulty laying eggs, other chickens tend to peck at them, etc. This afternoon we cleaned her up and put her in isolation in a dark shed to slow down egglaying and give her a chance to heal.
Update: Yesterday she looked about the same. She laid an egg which doesn't help. Today there seems to be less swelling, so I hope she's healing up.